# startIndex The position of the first element in a non-empty collection. ``` var startIndex: LazyFilterSequence.Index { get } ``` ## Discussion In an empty collection, `startIndex == endIndex`. > Complexity: O(*n*), where *n* is the ratio between unfiltered and > filtered collection counts. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)